1. Field of the Invention
This invention relates to hot fill plastic containers, and more particularly, to such containers having an improved label mount area in the body portion.
2. Description of the Related Technology
The use of blow molded plastic containers for packaging "hot fill" beverages is well known. However, a container that is used for hot fill applications is subject to additional mechanical stresses on the container that result in the container being more likely to fail during storage or handling. For example, it has been found that the thin sidewalls of the container deform or collapse as the container is being filled with hot fluids. In addition, the rigidity of the container decreases immediately after the hot fill liquid is introduced into the container. As the liquid cools, the liquid shrinks in volume which, in turn, produces a negative pressure or vacuum in the container. The container must be able to withstand such changes in pressure without failure.
As described in U.S. Pat. No. 5,337,909, hot fill containers typically comprise substantially rectangular vacuum panels that are designed to collapse inwardly after the container has been filled with hot liquid. However, the inward flexing of the panels caused by the hot fill vacuum creates high stress points at the top and bottom edges of the pressure panels, especially at the upper and lower corners of the panels. These stress points weaken the portions of the sidewall near the edges of the panels, allowing the sidewall to collapse inwardly during handling of the container or when containers are stacked together.
The hot-fill container disclosed in U.S. Pat. No. 5,337,909 has annular reinforcement ribs that extend continuously around the circumference of the container sidewall. It is stated that the reinforcement ribs support the vacuum panels at their upper and lower edges, holding the edges fixed, while permitting the center portions of the vacuum panels to flex inwardly while the bottle is being filled and to resist deformation of the vacuum panels subsequent to inward flexing of the vacuum panels due to filling and sealing of the container. FIGS. 5 and 6 depict an embodiment wherein the reinforcement ribs merge with the edges of the vacuum panels at the edge of the label upper and lower mounting panels.
Another hot-fill container having reinforcement ribs is disclosed in WO 97/34808. The container described in 97/34808 comprises a label mounting area having an upper and lower series of peripherally spaced, short, horizontal ribs separated endwise by label mount areas. It is stated that each upper and lower rib is located within the label mount section and is centered above or below, respectively, one of the lands. The container further comprises several rectangular vacuum panels that also experience high stress point at the corners of the collapse panels. It is further stated that the ribs stiffen the container adjacent lower corners 46 of the collapse panels.
It is an object of the present invention to provide a hot-filled, blow molded, plastic container which provides improved vacuum panels that minimize the stress points on the corners of the vacuum panels, by substantially removing these stress points, and thereby provide lower failure rates.
It is another object of the invention to provide a hot fill bottle having vacuum panels with sufficient reinforcement and support means.
It is another object of the invention to provide a hot fill bottle that maximizes the areas of contact between the label and the label mounting areas.